1. Field of Invention
The present invention relates generally to an engine fuel injection system, and more particularly to an electronic control common rail DME injection system.
2. Description of Related Arts
DME is known as a “green substitution fuel for diesel in 21st century”, but the DME is a gas at normal temperature and pressure, and has low viscosity, and poor sealing. The above characters cause sealing and abrasion problem in the plunger matching portions in the injection system, which is the difficult problem in application. Besides DME, the other low-viscosity fuels, such as liquefied petroleum gas (LPG), also have same low viscosity to cause the sealing and abrasion problem in the plunger matching portions in the injection system. The US006119664A patent of AVL company disclosed a common rail electronic control injection system using a low-viscosity fuel. The system comprises a high-pressure pump, a common rail tube, an electronic control injector, an electronic control unit, wherein the fuel is pressed to 200-350 bar by the high-pressure pump and is sent into the common rail tube, a two-position three-way solenoid valve is disposed between the common rail tube and the electronic control injector, the electronic control injector begins to inject when the common rail tube is connected with the electronic control injector via the two-position three-way solenoid valve, and the electronic control injector stops injecting when the two-position three-way solenoid valve is connected with a returning tube. The disadvantage of this design is that the sealing and abrasion problem in the plunger matching portions is inevitable because DME is directly pressed by the high-pressure pump.